1. Field of the Invention
The present invention relates to a wire bonding apparatus, and more particularly to a wire bonding apparatus with a bonding wire detector which detects a wire supply, wire breakage, improper wire connection, wire supply depletion, presence or absence of wire at the start of bonding, etc.
2. Prior Art
In conventional wire bonding apparatus disclosed for example in Japanese Patent Application Laid-Open No. 59-115533, an air guide is provided between a spool on which the bonding wire is wound and a bonding tool. The air guide blows air against the bonding wire so that tension is applied to the wire. A detection plate faces the direction that the air so that it contacts the bonding wire. Accordingly, the condition of the bonding wire is detected by determining whether or not the bonding wire is in contact with the detection plate. In other words, the condition of the bonding wire is ascertained in relation to whether or not an electrical current flows through the detection plate and to the bonding wire.
Thus, in the above described prior art, contact of the bonding wire with the detection plate is ascertained by determining whether or not an electrical current flows through the bonding wire. Accordingly, when the detection plate is soiled or when minute dust particles adhere to the bonding wire, it is impossible to accurately detect if the bonding wire is in contact with the detection plate. This causes operation error to occur.
More specifically, improper or proper detection of the wire supply is usually performed after completion of the second bonding step. The bonding wire is supplied by a motor which drives the spool until the wire contacts the detection plate. Accordingly, if electrical continuity does not exist between the detection plate and the bonding wire, even though the wire on the spool is in physical contact with the detection plate, the apparatus will erroneously indicate that the wire supply is improper, and wire will be excessively supplied resulting in slack. If, however, wire abnormalities such as wire breakage, improper wire connection or depletion of the wire supply, etc., are erroneously detected despite the fact that the bonding process is actually proceeding normally, the apparatus will stop.